Boron-Containing Systems

Boron. Neutral boron-containing systems with a //-electron doublet (heterocyclic counterparts of the cyclopropenyl cation55 are called borirenes (64—66, Scheme 32) and azadiboriridines (67, Scheme 33)80 81 Scheme 32. Borirenes... 

Although technically a heteroelement rather than a metal, some interesting Lewis acidic receptors for anions have been based on boron-containing systems. The first evidence for this type of anion receptor was published in 1967, one of the earliest examples of anion binding. Compound 21, when compared with 22, exhibited a chelate effect in the binding of methoxide anions (3). 

In boron-containing systems the initial Si3N4-crystallization without decomposition may indicate that the carbon is not present in the form of a reactive free carbon boron may keep carbon in some other (amorphous ) form to suppress or to retard... 

Kuz ma, Yu.B., and N.F. Chaban, 1990, Binary and Ternary Boron Containing Systems, Referenee Book (Metallurgiya, Moscow) 320pp. In Russian. 

In an analogous fashion to the hydroboration reaction, a variety of boron-containing substrates react with iminoboranes. Addition of X2B—Cl, X2B—N3, X2B—SR, X2B—NR2, and X2B—R to the unsaturated B—N system is called chloro-, azido-, thio-, amino-, and alkyloboration, respectively. The azidoboration and chloroboration of two iminoboranes are shown ia equations 23 and 24 (72). 

B. Polymers Containing Boron Ring Systems in the Backbone... 

The best known boron-containing ring systems are the so-called inorganic benzenes, namely, borazine (71), boroxine (72), and triphosphatriborin (73) (Fig. 46), which are isoelectronic and isostructural with benzene. These ring systems are obtained by the interaction of boron with nitrogen, oxygen, and phosphorus, respectively.4... 

The area of organoboron polymers containing borazine and its derivatives is covered in Chapter 5 of this book by Miele and co-workers. Miele and Bernard also describe the utilization of these polymers in ceramics, fibers, and so on, in Chapter 3 of this book. In this section, the utilization of polymers containing borazine or in some cases the bicyclic boron ligand, 9-BBN, for the production of SiC or Si/C/B fibers is briefly described. Recent advances in polypyrazolylborate or pyrazabole-containing polymers and other boron ring system-derived polymers also have been briefly described. 

In Chapter 8.34 of CHEC-II(1996) synthesis and properties of the boron-containing heterocycles with ring junction boron atom 1-6 have been considered <1996CHEC-II(8)889>. However, only a few papers have been published during the last decade concerning the systems 1-4 (Figure 1) and so they are discussed in Section 12.13.6. 

Philp, D. Dynamic Covalent Chemistry of Boron-Containing Heteroaromatic Systems. Proceedings of the 233rd American Chemical Society National Meeting, Chicago, IL, March 25-29. 2007. 

Today, there exist a wide variety of boron-containing polymers including ring systems such as borazines (structure 11.41), boroxines (structure 11.42), and triphosphatoborins (structure 11.43),... 

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